<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>小于768</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        li{
            list-style: none;
            float: left;
            width: 33.33%;
            height: 40px;
            line-height: 40px;
            text-align: center;
            background-color: green;
        }
        .container{
            width: 100%;
        }
    </style>
</head>
<body>
    <div class="container">
        <ul>
            <li>导航</li>
            <li>导航</li>
            <li>导航</li>
            <li>导航</li>
            <li>导航</li>
            <li>导航</li>
            <li>导航</li>
            <li>导航</li>
        </ul>
    </div>
</body>
</html>